Is Validity All That You Need?
You have seen that validity ensures structural constraints, but does that guarantee that those you exchange information with will know how to use your data? Not necessarily! All that validity ensures is the structure of the data in your XML instance, it is up to the application to determine how those data will be manipulated or processed further. Even if you publish your schema along with your XML document, those two pieces alone are not sufficient to complete an application of those data to solve a business problem.
Another typical misconception is that a schema is essential to conducting business over the Web with XML. A schema is a good method, but not the only method of ensuring the integrity of data that is generated for use by XML. One major advantage to using schemata in conjunction with XML documents to help control machine-generated content, improve searching, or validate data structures is that they are designed for that purpose. On later days, you will use programming techniques to manipulate data without having to build the logic pertaining to validity if a schema is associated with your XML documents.